Millions of people suffer from abnormally high heart beat rhythm, a condition referred to as "tachycardia." One type of tachycardia is right sided supra-ventricular tachycardia (SVT). This condition is caused by a conducting pathway between the right atrium at the right ventricle across the tricuspid annulus. With right sided supra-ventricular tachycardia, the atria typically beats too rapidly. Symptoms of right sided supra-ventricular tachycardia include chest pain, fatigue and dizziness.
Radiofrequency (RF) catheter ablation has been found to be a safe and efficacious means of interrupting accessory electrical pathways which result in tachycardia. In such a procedure, a special electrophysiology catheter is guided through a vein into the patient's heart and to the site of the accessory pathway. The catheter is designed to transmit energy from an external source into the accessory pathway in an amount sufficient to ablate the tissue. The ablated tissue is replaced with scar tissue which interrupts the accessory pathway. The normal conduction of electroactivity is thereby restored.
Before an RF catheter ablation procedure can be utilized, the site of the accessory pathway must be determined. This is accomplished with a diagnostic or mapping catheter which typically comprises multiple electrodes for stimulating and sensing electrical activity. In, general, this procedure involves introducing a mapping catheter into the patient's heart and into the chamber where the arrhythmia condition exists. The tissue is stimulated in a manner intended to induce the arrhythmia and expose the abnormal electrical conduction. The resulting information regarding the number and locations of aberrant sites identified and the severity of the abnormality enables the electrophysiologists to determine the appropriate course of treatment. Electrophysiologic evaluation generally involves multiple tests to diagnose the arrhythmia and to assess the potential effectiveness of various treatment strategies.
One procedure for determining the site of right sided supra-ventricular tachycardia is to introduce a mapping catheter into the right coronary artery which extends about the right atrium at about the location of the tricuspid annulus. This procedure is very dangerous and accordingly not favored. Another known procedure is to introduce a deflectable tip mapping catheter into the right atrium and, by manipulation of the catheter, to move the catheter about, particularly around the tricuspid annulus until the accessory pathway is located. This is a time-consuming and cumbersome approach.
An improvement in mapping the right sided supra-ventricular pathways has been the use of a multiple electrode catheter having a generally circular precurved tip portion. Such a catheter is advanced from the femoral vein by Seldinger technique into the right atrium. The distal end of the tip portion is maneuvered into the coronary sinus (C.S.) ostium and the remainder of the circular tip portion is maneuvered into the region of the tricuspid annulus. Through the use of multiple electrodes around the circular tip portion, the time required to map the right sided supra-ventricular pathways is greatly reduced.
While the use of a generally circular tip portion has greatly improved the efficiency of the mapping procedure for right sided supra-ventricular pathways, there are still some difficulties associated with this procedure. First, the circular tip portion of the catheter is difficult to maneuver. Secondly, the diameter of the generally circular tip portion is fixed and therefore cannot be adjusted to accommodate atrial chambers of varying sizes. The catheter tip is also difficult to maneuver, particularly being difficult to anchor the distal end of the tip portion in the CS ostium.